/**
 * Copyright 2009-2016 the original author or authors.
 * <p>
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 * <p>
 * http://www.apache.org/licenses/LICENSE-2.0
 * <p>
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
package com.baomidou.mybatisplus;

import com.baomidou.mybatisplus.entity.GlobalConfiguration;
import com.baomidou.mybatisplus.mapper.BaseMapper;
import org.apache.ibatis.annotations.Arg;
import org.apache.ibatis.annotations.CacheNamespace;
import org.apache.ibatis.annotations.CacheNamespaceRef;
import org.apache.ibatis.annotations.Case;
import org.apache.ibatis.annotations.ConstructorArgs;
import org.apache.ibatis.annotations.Delete;
import org.apache.ibatis.annotations.DeleteProvider;
import org.apache.ibatis.annotations.Insert;
import org.apache.ibatis.annotations.InsertProvider;
import org.apache.ibatis.annotations.Lang;
import org.apache.ibatis.annotations.MapKey;
import org.apache.ibatis.annotations.Options;
import org.apache.ibatis.annotations.Options.FlushCachePolicy;
import org.apache.ibatis.annotations.Property;
import org.apache.ibatis.annotations.Result;
import org.apache.ibatis.annotations.ResultMap;
import org.apache.ibatis.annotations.ResultType;
import org.apache.ibatis.annotations.Results;
import org.apache.ibatis.annotations.Select;
import org.apache.ibatis.annotations.SelectKey;
import org.apache.ibatis.annotations.SelectProvider;
import org.apache.ibatis.annotations.TypeDiscriminator;
import org.apache.ibatis.annotations.Update;
import org.apache.ibatis.annotations.UpdateProvider;
import org.apache.ibatis.binding.BindingException;
import org.apache.ibatis.binding.MapperMethod.ParamMap;
import org.apache.ibatis.builder.BuilderException;
import org.apache.ibatis.builder.IncompleteElementException;
import org.apache.ibatis.builder.MapperBuilderAssistant;
import org.apache.ibatis.builder.annotation.MapperAnnotationBuilder;
import org.apache.ibatis.builder.annotation.MethodResolver;
import org.apache.ibatis.builder.annotation.ProviderSqlSource;
import org.apache.ibatis.cursor.Cursor;
import org.apache.ibatis.executor.keygen.Jdbc3KeyGenerator;
import org.apache.ibatis.executor.keygen.KeyGenerator;
import org.apache.ibatis.executor.keygen.NoKeyGenerator;
import org.apache.ibatis.executor.keygen.SelectKeyGenerator;
import org.apache.ibatis.io.Resources;
import org.apache.ibatis.mapping.Discriminator;
import org.apache.ibatis.mapping.FetchType;
import org.apache.ibatis.mapping.MappedStatement;
import org.apache.ibatis.mapping.ResultFlag;
import org.apache.ibatis.mapping.ResultMapping;
import org.apache.ibatis.mapping.ResultSetType;
import org.apache.ibatis.mapping.SqlCommandType;
import org.apache.ibatis.mapping.SqlSource;
import org.apache.ibatis.mapping.StatementType;
import org.apache.ibatis.parsing.PropertyParser;
import org.apache.ibatis.reflection.TypeParameterResolver;
import org.apache.ibatis.scripting.LanguageDriver;
import org.apache.ibatis.session.Configuration;
import org.apache.ibatis.session.ResultHandler;
import org.apache.ibatis.session.RowBounds;
import org.apache.ibatis.type.JdbcType;
import org.apache.ibatis.type.TypeHandler;
import org.apache.ibatis.type.UnknownTypeHandler;

import java.io.IOException;
import java.io.InputStream;
import java.lang.annotation.Annotation;
import java.lang.reflect.Array;
import java.lang.reflect.GenericArrayType;
import java.lang.reflect.Method;
import java.lang.reflect.ParameterizedType;
import java.lang.reflect.Type;
import java.util.ArrayList;
import java.util.Collection;
import java.util.HashMap;
import java.util.HashSet;
import java.util.Iterator;
import java.util.List;
import java.util.Locale;
import java.util.Map;
import java.util.Properties;
import java.util.Set;

/**
 * <p>
 * 继承 MapperAnnotationBuilder 没有XML配置文件注入基础CRUD方法
 * </p>
 * 
 * @author Caratacus
 * @Date 2017-01-04
 */
public class MybatisMapperAnnotationBuilder extends MapperAnnotationBuilder {

	private final Set<Class<? extends Annotation>> sqlAnnotationTypes = new HashSet<Class<? extends Annotation>>();
	private final Set<Class<? extends Annotation>> sqlProviderAnnotationTypes = new HashSet<Class<? extends Annotation>>();

	private Configuration configuration;
	private MapperBuilderAssistant assistant;
	private Class<?> type;

	public MybatisMapperAnnotationBuilder(Configuration configuration, Class<?> type) {
		super(configuration, type);
		String resource = type.getName().replace('.', '/') + ".java (best guess)";
		this.assistant = new MapperBuilderAssistant(configuration, resource);
		this.configuration = configuration;
		this.type = type;
		sqlAnnotationTypes.add(Select.class);
		sqlAnnotationTypes.add(Insert.class);
		sqlAnnotationTypes.add(Update.class);
		sqlAnnotationTypes.add(Delete.class);
		sqlProviderAnnotationTypes.add(SelectProvider.class);
		sqlProviderAnnotationTypes.add(InsertProvider.class);
		sqlProviderAnnotationTypes.add(UpdateProvider.class);
		sqlProviderAnnotationTypes.add(DeleteProvider.class);
	}

	public void parse() {
		String resource = type.toString();
		if (!configuration.isResourceLoaded(resource)) {
			boolean existXml = loadXmlResource();
			configuration.addLoadedResource(resource);
			assistant.setCurrentNamespace(type.getName());
			parseCache();
			parseCacheRef();
			Method[] methods = type.getMethods();
			// TODO 注入存在 xxMapper.xml CURD (应该在注解之前注入)
			inspectInject(existXml);
			for (Method method : methods) {
				try {
					// issue #237
					if (!method.isBridge()) {
						parseStatement(method);
					}
				} catch (IncompleteElementException e) {
					configuration.addIncompleteMethod(new MethodResolver(this, method));
				}
			}

		}
		parsePendingMethods();
	}

	/*
	 * 注入 CURD 动态 SQL(XML不存在时注入)
	 */
	private void inspectInject(boolean flag) {
		if (!flag && BaseMapper.class.isAssignableFrom(type)) {
			GlobalConfiguration.getSqlInjector(configuration).inspectInject(assistant, type);
		}
	}

	private void parsePendingMethods() {
		Collection<MethodResolver> incompleteMethods = configuration.getIncompleteMethods();
		synchronized (incompleteMethods) {
			Iterator<MethodResolver> iter = incompleteMethods.iterator();
			while (iter.hasNext()) {
				try {
					iter.next().resolve();
					iter.remove();
				} catch (IncompleteElementException e) {
					// This method is still missing a resource
				}
			}
		}
	}

	/**
	 * 是否存在XML(该方法并不能客观的判断resource的路径,只是Mybatis默认认为的xml路径)
	 *
	 * @return boolean ture存在,flase不存在
	 */
	// TODO 该方法改为返回 boolean 判断是否存在 xxxMapper.xml
	private boolean loadXmlResource() {
		boolean flag = true;
		// Spring may not know the real resource name so we check a flag
		// to prevent loading again a resource twice
		// this flag is set at MybatisXMLMapperBuilder#bindMapperForNamespace
		if (!configuration.isResourceLoaded("namespace:" + type.getName())) {
			String xmlResource = type.getName().replace('.', '/') + ".xml";
			InputStream inputStream = null;
			try {
				inputStream = Resources.getResourceAsStream(type.getClassLoader(), xmlResource);
			} catch (IOException e) {
				// ignore, resource is not required
				flag = false;
			}
			if (inputStream != null) {
				MybatisXMLMapperBuilder xmlParser = new MybatisXMLMapperBuilder(inputStream, assistant.getConfiguration(),
						xmlResource, configuration.getSqlFragments(), type.getName());
				xmlParser.parse();
			}
		}
		return flag;
	}

	private void parseCache() {
		CacheNamespace cacheDomain = type.getAnnotation(CacheNamespace.class);
		if (cacheDomain != null) {
			Integer size = cacheDomain.size() == 0 ? null : cacheDomain.size();
			Long flushInterval = cacheDomain.flushInterval() == 0 ? null : cacheDomain.flushInterval();
			Properties props = convertToProperties(cacheDomain.properties());
			assistant.useNewCache(cacheDomain.implementation(), cacheDomain.eviction(), flushInterval, size,
					cacheDomain.readWrite(), cacheDomain.blocking(), props);
		}
	}

	private Properties convertToProperties(Property[] properties) {
		if (properties.length == 0) {
			return null;
		}
		Properties props = new Properties();
		for (Property property : properties) {
			props.setProperty(property.name(), PropertyParser.parse(property.value(), configuration.getVariables()));
		}
		return props;
	}

	private void parseCacheRef() {
		CacheNamespaceRef cacheDomainRef = type.getAnnotation(CacheNamespaceRef.class);
		if (cacheDomainRef != null) {
			Class<?> refType = cacheDomainRef.value();
			String refName = cacheDomainRef.name();
			if (refType == void.class && refName.isEmpty()) {
				throw new BuilderException("Should be specified either value() or name() attribute in the @CacheNamespaceRef");
			}
			if (refType != void.class && !refName.isEmpty()) {
				throw new BuilderException("Cannot use both value() and name() attribute in the @CacheNamespaceRef");
			}
			String namespace = (refType != void.class) ? refType.getName() : refName;
			assistant.useCacheRef(namespace);
		}
	}

	private String parseResultMap(Method method) {
		Class<?> returnType = getReturnType(method);
		ConstructorArgs args = method.getAnnotation(ConstructorArgs.class);
		Results results = method.getAnnotation(Results.class);
		TypeDiscriminator typeDiscriminator = method.getAnnotation(TypeDiscriminator.class);
		String resultMapId = generateResultMapName(method);
		applyResultMap(resultMapId, returnType, argsIf(args), resultsIf(results), typeDiscriminator);
		return resultMapId;
	}

	private String generateResultMapName(Method method) {
		Results results = method.getAnnotation(Results.class);
		if (results != null && !results.id().isEmpty()) {
			return type.getName() + "." + results.id();
		}
		StringBuilder suffix = new StringBuilder();
		for (Class<?> c : method.getParameterTypes()) {
			suffix.append("-");
			suffix.append(c.getSimpleName());
		}
		if (suffix.length() < 1) {
			suffix.append("-void");
		}
		return type.getName() + "." + method.getName() + suffix;
	}

	private void applyResultMap(String resultMapId, Class<?> returnType, Arg[] args, Result[] results,
			TypeDiscriminator discriminator) {
		List<ResultMapping> resultMappings = new ArrayList<ResultMapping>();
		applyConstructorArgs(args, returnType, resultMappings);
		applyResults(results, returnType, resultMappings);
		Discriminator disc = applyDiscriminator(resultMapId, returnType, discriminator);
		// TODO add AutoMappingBehaviour
		assistant.addResultMap(resultMapId, returnType, null, disc, resultMappings, null);
		createDiscriminatorResultMaps(resultMapId, returnType, discriminator);
	}

	private void createDiscriminatorResultMaps(String resultMapId, Class<?> resultType, TypeDiscriminator discriminator) {
		if (discriminator != null) {
			for (Case c : discriminator.cases()) {
				String caseResultMapId = resultMapId + "-" + c.value();
				List<ResultMapping> resultMappings = new ArrayList<ResultMapping>();
				// issue #136
				applyConstructorArgs(c.constructArgs(), resultType, resultMappings);
				applyResults(c.results(), resultType, resultMappings);
				// TODO add AutoMappingBehaviour
				assistant.addResultMap(caseResultMapId, c.type(), resultMapId, null, resultMappings, null);
			}
		}
	}

	private Discriminator applyDiscriminator(String resultMapId, Class<?> resultType, TypeDiscriminator discriminator) {
		if (discriminator != null) {
			String column = discriminator.column();
			Class<?> javaType = discriminator.javaType() == void.class ? String.class : discriminator.javaType();
			JdbcType jdbcType = discriminator.jdbcType() == JdbcType.UNDEFINED ? null : discriminator.jdbcType();
			@SuppressWarnings("unchecked")
			Class<? extends TypeHandler<?>> typeHandler = (Class<? extends TypeHandler<?>>) (discriminator.typeHandler() == UnknownTypeHandler.class ? null
					: discriminator.typeHandler());
			Case[] cases = discriminator.cases();
			Map<String, String> discriminatorMap = new HashMap<String, String>();
			for (Case c : cases) {
				String value = c.value();
				String caseResultMapId = resultMapId + "-" + value;
				discriminatorMap.put(value, caseResultMapId);
			}
			return assistant.buildDiscriminator(resultType, column, javaType, jdbcType, typeHandler, discriminatorMap);
		}
		return null;
	}

	void parseStatement(Method method) {
		Class<?> parameterTypeClass = getParameterType(method);
		LanguageDriver languageDriver = getLanguageDriver(method);
		SqlSource sqlSource = getSqlSourceFromAnnotations(method, parameterTypeClass, languageDriver);
		if (sqlSource != null) {
			Options options = method.getAnnotation(Options.class);
			final String mappedStatementId = type.getName() + "." + method.getName();
			Integer fetchSize = null;
			Integer timeout = null;
			StatementType statementType = StatementType.PREPARED;
			ResultSetType resultSetType = ResultSetType.FORWARD_ONLY;
			SqlCommandType sqlCommandType = getSqlCommandType(method);
			boolean isSelect = sqlCommandType == SqlCommandType.SELECT;
			boolean flushCache = !isSelect;
			boolean useCache = isSelect;

			KeyGenerator keyGenerator;
			String keyProperty = "id";
			String keyColumn = null;
			if (SqlCommandType.INSERT.equals(sqlCommandType) || SqlCommandType.UPDATE.equals(sqlCommandType)) {
				// first check for SelectKey annotation - that overrides
				// everything else
				SelectKey selectKey = method.getAnnotation(SelectKey.class);
				if (selectKey != null) {
					keyGenerator = handleSelectKeyAnnotation(selectKey, mappedStatementId, getParameterType(method),
							languageDriver);
					keyProperty = selectKey.keyProperty();
				} else if (options == null) {
					keyGenerator = configuration.isUseGeneratedKeys() ? new Jdbc3KeyGenerator() : new NoKeyGenerator();
				} else {
					keyGenerator = options.useGeneratedKeys() ? new Jdbc3KeyGenerator() : new NoKeyGenerator();
					keyProperty = options.keyProperty();
					keyColumn = options.keyColumn();
				}
			} else {
				keyGenerator = new NoKeyGenerator();
			}

			if (options != null) {
				if (FlushCachePolicy.TRUE.equals(options.flushCache())) {
					flushCache = true;
				} else if (FlushCachePolicy.FALSE.equals(options.flushCache())) {
					flushCache = false;
				}
				useCache = options.useCache();
				fetchSize = options.fetchSize() > -1 || options.fetchSize() == Integer.MIN_VALUE ? options.fetchSize() : null; // issue
																																// #348
				timeout = options.timeout() > -1 ? options.timeout() : null;
				statementType = options.statementType();
				resultSetType = options.resultSetType();
			}

			String resultMapId = null;
			ResultMap resultMapAnnotation = method.getAnnotation(ResultMap.class);
			if (resultMapAnnotation != null) {
				String[] resultMaps = resultMapAnnotation.value();
				StringBuilder sb = new StringBuilder();
				for (String resultMap : resultMaps) {
					if (sb.length() > 0) {
						sb.append(",");
					}
					sb.append(resultMap);
				}
				resultMapId = sb.toString();
			} else if (isSelect) {
				resultMapId = parseResultMap(method);
			}

			assistant.addMappedStatement(mappedStatementId, sqlSource, statementType, sqlCommandType, fetchSize, timeout,
			// ParameterMapID
					null, parameterTypeClass, resultMapId, getReturnType(method), resultSetType, flushCache, useCache,
					// TODO gcode issue #577
					false, keyGenerator, keyProperty, keyColumn,
					// DatabaseID
					null, languageDriver,
					// ResultSets
					options != null ? nullOrEmpty(options.resultSets()) : null);
		}
	}

	private LanguageDriver getLanguageDriver(Method method) {
		Lang lang = method.getAnnotation(Lang.class);
		Class<?> langClass = null;
		if (lang != null) {
			langClass = lang.value();
		}
		return assistant.getLanguageDriver(langClass);
	}

	private Class<?> getParameterType(Method method) {
		Class<?> parameterType = null;
		Class<?>[] parameterTypes = method.getParameterTypes();
		for (Class<?> currentParameterType : parameterTypes) {
			if (!RowBounds.class.isAssignableFrom(currentParameterType)
					&& !ResultHandler.class.isAssignableFrom(currentParameterType)) {
				if (parameterType == null) {
					parameterType = currentParameterType;
				} else {
					// issue #135
					parameterType = ParamMap.class;
				}
			}
		}
		return parameterType;
	}

	private Class<?> getReturnType(Method method) {
		Class<?> returnType = method.getReturnType();
		Type resolvedReturnType = TypeParameterResolver.resolveReturnType(method, type);
		if (resolvedReturnType instanceof Class) {
			returnType = (Class<?>) resolvedReturnType;
			if (returnType.isArray()) {
				returnType = returnType.getComponentType();
			}
			// gcode issue #508
			if (void.class.equals(returnType)) {
				ResultType rt = method.getAnnotation(ResultType.class);
				if (rt != null) {
					returnType = rt.value();
				}
			}
		} else if (resolvedReturnType instanceof ParameterizedType) {
			ParameterizedType parameterizedType = (ParameterizedType) resolvedReturnType;
			Class<?> rawType = (Class<?>) parameterizedType.getRawType();
			if (Collection.class.isAssignableFrom(rawType) || Cursor.class.isAssignableFrom(rawType)) {
				Type[] actualTypeArguments = parameterizedType.getActualTypeArguments();
				if (actualTypeArguments != null && actualTypeArguments.length == 1) {
					Type returnTypeParameter = actualTypeArguments[0];
					if (returnTypeParameter instanceof Class<?>) {
						returnType = (Class<?>) returnTypeParameter;
					} else if (returnTypeParameter instanceof ParameterizedType) {
						// (gcode issue #443) actual type can be a also a
						// parameterized type
						returnType = (Class<?>) ((ParameterizedType) returnTypeParameter).getRawType();
					} else if (returnTypeParameter instanceof GenericArrayType) {
						Class<?> componentType = (Class<?>) ((GenericArrayType) returnTypeParameter).getGenericComponentType();
						// (gcode issue #525) support List<byte[]>
						returnType = Array.newInstance(componentType, 0).getClass();
					}
				}
			} else if (method.isAnnotationPresent(MapKey.class) && Map.class.isAssignableFrom(rawType)) {
				// (gcode issue 504) Do not look into Maps if there is not
				// MapKey annotation
				Type[] actualTypeArguments = parameterizedType.getActualTypeArguments();
				if (actualTypeArguments != null && actualTypeArguments.length == 2) {
					Type returnTypeParameter = actualTypeArguments[1];
					if (returnTypeParameter instanceof Class<?>) {
						returnType = (Class<?>) returnTypeParameter;
					} else if (returnTypeParameter instanceof ParameterizedType) {
						// (gcode issue 443) actual type can be a also a
						// parameterized type
						returnType = (Class<?>) ((ParameterizedType) returnTypeParameter).getRawType();
					}
				}
			}
		}

		return returnType;
	}

	private SqlSource getSqlSourceFromAnnotations(Method method, Class<?> parameterType, LanguageDriver languageDriver) {
		try {
			Class<? extends Annotation> sqlAnnotationType = getSqlAnnotationType(method);
			Class<? extends Annotation> sqlProviderAnnotationType = getSqlProviderAnnotationType(method);
			if (sqlAnnotationType != null) {
				if (sqlProviderAnnotationType != null) {
					throw new BindingException("You cannot supply both a static SQL and SqlProvider to method named "
							+ method.getName());
				}
				Annotation sqlAnnotation = method.getAnnotation(sqlAnnotationType);
				final String[] strings = (String[]) sqlAnnotation.getClass().getMethod("value").invoke(sqlAnnotation);
				return buildSqlSourceFromStrings(strings, parameterType, languageDriver);
			} else if (sqlProviderAnnotationType != null) {
				Annotation sqlProviderAnnotation = method.getAnnotation(sqlProviderAnnotationType);
				return new ProviderSqlSource(assistant.getConfiguration(), sqlProviderAnnotation);
			}
			return null;
		} catch (Exception e) {
			throw new BuilderException("Could not find value method on SQL annotation.  Cause: " + e, e);
		}
	}

	private SqlSource buildSqlSourceFromStrings(String[] strings, Class<?> parameterTypeClass, LanguageDriver languageDriver) {
		final StringBuilder sql = new StringBuilder();
		for (String fragment : strings) {
			sql.append(fragment);
			sql.append(" ");
		}
		return languageDriver.createSqlSource(configuration, sql.toString().trim(), parameterTypeClass);
	}

	private SqlCommandType getSqlCommandType(Method method) {
		Class<? extends Annotation> type = getSqlAnnotationType(method);

		if (type == null) {
			type = getSqlProviderAnnotationType(method);

			if (type == null) {
				return SqlCommandType.UNKNOWN;
			}

			if (type == SelectProvider.class) {
				type = Select.class;
			} else if (type == InsertProvider.class) {
				type = Insert.class;
			} else if (type == UpdateProvider.class) {
				type = Update.class;
			} else if (type == DeleteProvider.class) {
				type = Delete.class;
			}
		}

		return SqlCommandType.valueOf(type.getSimpleName().toUpperCase(Locale.ENGLISH));
	}

	private Class<? extends Annotation> getSqlAnnotationType(Method method) {
		return chooseAnnotationType(method, sqlAnnotationTypes);
	}

	private Class<? extends Annotation> getSqlProviderAnnotationType(Method method) {
		return chooseAnnotationType(method, sqlProviderAnnotationTypes);
	}

	private Class<? extends Annotation> chooseAnnotationType(Method method, Set<Class<? extends Annotation>> types) {
		for (Class<? extends Annotation> type : types) {
			Annotation annotation = method.getAnnotation(type);
			if (annotation != null) {
				return type;
			}
		}
		return null;
	}

	private void applyResults(Result[] results, Class<?> resultType, List<ResultMapping> resultMappings) {
		for (Result result : results) {
			List<ResultFlag> flags = new ArrayList<ResultFlag>();
			if (result.id()) {
				flags.add(ResultFlag.ID);
			}
			@SuppressWarnings("unchecked")
			Class<? extends TypeHandler<?>> typeHandler = (Class<? extends TypeHandler<?>>) ((result.typeHandler() == UnknownTypeHandler.class) ? null
					: result.typeHandler());
			ResultMapping resultMapping = assistant.buildResultMapping(resultType, nullOrEmpty(result.property()),
					nullOrEmpty(result.column()), result.javaType() == void.class ? null : result.javaType(),
					result.jdbcType() == JdbcType.UNDEFINED ? null : result.jdbcType(),
					hasNestedSelect(result) ? nestedSelectId(result) : null, null, null, null, typeHandler, flags, null, null,
					isLazy(result));
			resultMappings.add(resultMapping);
		}
	}

	private String nestedSelectId(Result result) {
		String nestedSelect = result.one().select();
		if (nestedSelect.length() < 1) {
			nestedSelect = result.many().select();
		}
		if (!nestedSelect.contains(".")) {
			nestedSelect = type.getName() + "." + nestedSelect;
		}
		return nestedSelect;
	}

	private boolean isLazy(Result result) {
		boolean isLazy = configuration.isLazyLoadingEnabled();
		if (result.one().select().length() > 0 && FetchType.DEFAULT != result.one().fetchType()) {
			isLazy = (result.one().fetchType() == FetchType.LAZY);
		} else if (result.many().select().length() > 0 && FetchType.DEFAULT != result.many().fetchType()) {
			isLazy = (result.many().fetchType() == FetchType.LAZY);
		}
		return isLazy;
	}

	private boolean hasNestedSelect(Result result) {
		if (result.one().select().length() > 0 && result.many().select().length() > 0) {
			throw new BuilderException("Cannot use both @One and @Many annotations in the same @Result");
		}
		return result.one().select().length() > 0 || result.many().select().length() > 0;
	}

	private void applyConstructorArgs(Arg[] args, Class<?> resultType, List<ResultMapping> resultMappings) {
		for (Arg arg : args) {
			List<ResultFlag> flags = new ArrayList<ResultFlag>();
			flags.add(ResultFlag.CONSTRUCTOR);
			if (arg.id()) {
				flags.add(ResultFlag.ID);
			}
			@SuppressWarnings("unchecked")
			Class<? extends TypeHandler<?>> typeHandler = (Class<? extends TypeHandler<?>>) (arg.typeHandler() == UnknownTypeHandler.class ? null
					: arg.typeHandler());
			ResultMapping resultMapping = assistant.buildResultMapping(resultType, null, nullOrEmpty(arg.column()),
					arg.javaType() == void.class ? null : arg.javaType(),
					arg.jdbcType() == JdbcType.UNDEFINED ? null : arg.jdbcType(), nullOrEmpty(arg.select()),
					nullOrEmpty(arg.resultMap()), null, null, typeHandler, flags, null, null, false);
			resultMappings.add(resultMapping);
		}
	}

	private String nullOrEmpty(String value) {
		return value == null || value.trim().length() == 0 ? null : value;
	}

	private Result[] resultsIf(Results results) {
		return results == null ? new Result[0] : results.value();
	}

	private Arg[] argsIf(ConstructorArgs args) {
		return args == null ? new Arg[0] : args.value();
	}

	private KeyGenerator handleSelectKeyAnnotation(SelectKey selectKeyAnnotation, String baseStatementId,
			Class<?> parameterTypeClass, LanguageDriver languageDriver) {
		String id = baseStatementId + SelectKeyGenerator.SELECT_KEY_SUFFIX;
		Class<?> resultTypeClass = selectKeyAnnotation.resultType();
		StatementType statementType = selectKeyAnnotation.statementType();
		String keyProperty = selectKeyAnnotation.keyProperty();
		String keyColumn = selectKeyAnnotation.keyColumn();
		boolean executeBefore = selectKeyAnnotation.before();

		// defaults
		boolean useCache = false;
		KeyGenerator keyGenerator = new NoKeyGenerator();
		Integer fetchSize = null;
		Integer timeout = null;
		boolean flushCache = false;
		String parameterMap = null;
		String resultMap = null;
		ResultSetType resultSetTypeEnum = null;

		SqlSource sqlSource = buildSqlSourceFromStrings(selectKeyAnnotation.statement(), parameterTypeClass, languageDriver);
		SqlCommandType sqlCommandType = SqlCommandType.SELECT;

		assistant.addMappedStatement(id, sqlSource, statementType, sqlCommandType, fetchSize, timeout, parameterMap,
				parameterTypeClass, resultMap, resultTypeClass, resultSetTypeEnum, flushCache, useCache, false, keyGenerator,
				keyProperty, keyColumn, null, languageDriver, null);

		id = assistant.applyCurrentNamespace(id, false);

		MappedStatement keyStatement = configuration.getMappedStatement(id, false);
		SelectKeyGenerator answer = new SelectKeyGenerator(keyStatement, executeBefore);
		configuration.addKeyGenerator(id, answer);
		return answer;
	}

}